Shell Programming and Scripting

 
echo "yes or no?"
read ans
 
case $ans in
 
[yY]*)
echo "yes"
;;
 
[nN]*)
echo "no"
;;
 
*)
echo "yes or no only"
#here, if the answer is not "Y" or "N", I want to go back to asking "yes or no?"
;;
esac

while [ 1 ]
do
    echo "yes or no?"
    read ans
    case $ans in
    [yY]es)
        echo "yes"
        # more statements
        break
        ;;
         
    [nN]o)
        echo "no"
        # more statements
        break
        ;;
    *)
        echo "yes or no only"
        ;;
    esac
done

yes()
{
        echo "Do something."
}
no()
{
        echo "Do something else."
}
while true
do
        # Your case code, remembering to call "yes" or "no" as commands...
        # Remember also to give yourself a getout clause...
done

while :

while [ 1 ]